Paper 2022/805

Authenticated Consensus in Synchronous Systems with Mixed Faults

Ittai Abraham, VMWare Research
Danny Dolev, Hebrew University of Jerusalem
Alon Kagan, Hebrew University of Jerusalem
Gilad Stern, Hebrew University of Jerusalem

Protocols solving authenticated consensus in synchronous networks with Byzantine faults have been widely researched and known to exists if and only if $n>2f$ for $f$ Byzantine faults. Similarly, protocols solving authenticated consensus in partially synchronous networks are known to exist if $n>3f+2k$ for $f$ Byzantine faults and $k$ crash faults. Currently, the only known synchronous protocol for consensus with a resilience of $n>2f+k$ is a binary consensus protocol. In this work we fill a natural gap in our knowledge by presenting MixSync, an authenticated multivalued consensus protocol in synchronous networks resilient to $f$ Byzantine faults and $k$ crash faults if $n>2f+k$. As a basic building block, we first define and then construct a publicly verifiable crusader agreement protocol with the same resilience. The protocol uses a simple double-send round to guarantee non-equivocation, a technique later used in the MixSync protocol. We then discuss how to construct a state machine replication protocol using these ideas, and how they can be used in general to make such protocols resilient to crash faults. Finally, we prove lower bounds showing that $n>2f+k$ is optimally resilient for consensus and state machine replication protocols.

Available format(s)
Cryptographic protocols
Publication info
consensus state machine replication mixed faults synchrony lower bounds
Contact author(s)
iabraham @ vmware com
danny dolev @ mail huji ac il
alon kagan @ mail huji ac il
gilad stern @ mail huji ac il
2022-09-05: revised
2022-06-21: received
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      author = {Ittai Abraham and Danny Dolev and Alon Kagan and Gilad Stern},
      title = {Authenticated Consensus in Synchronous Systems with Mixed Faults},
      howpublished = {Cryptology ePrint Archive, Paper 2022/805},
      year = {2022},
      note = {\url{}},
      url = {}
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